The invention relates to the use of compounds which are inhibitors of serine proteases. Proteases or proteolytic enzymes are essential in organisms, from bacteria and viruses to mammals. Proteases digest and degrade proteins by hydrolyzing peptide bonds. Serine proteases (EC. 3.4.21) have common features in the active site, primarily an active serine residue. There are two main types of serine proteases; the chymotrypsin/trypsin/elastase-like and subtilisin-like, which have an identical spatial arrangement of catalytic His, Asp, and Ser but in quite different protein scaffolds. However, over twenty families (S1-S27) of serine proteases have been identified that are grouped into 6 clans on the basis of structural similarity and other functional evidence, SA, SB, SC, SE, SF & SG. Family of chymotrypsin/trypsin/elastase-like serine proteases have been subdivided into two classes. The “large” class (ca 230 residues) includes mostly mammalian enzymes such as trypsin, chymotrypsin, elastase, kallikrein, and thrombin. The “small” class (ca 190 residues) includes the bacterial enzymes.
The catalytic His, Asp and Ser are flanked by substrate amino acid side chain residue binding pockets termed S1′, S2′, S3′ etc on the C-terminal or ‘prime’ side of the substrate and S1, S2, S3 etc on the N-terminal side. This nomenclature is as described in Structure and Mechanism in Protein Science: A Guide to Enzyme Catalysis and Protein Folding, Alan Fersht, 1999 (W.H. Freeman and Company) pages 40-43 and Brik et al, Org. Biomol. Chem., 2003, 1, 5-14. The chymotrypsin/trypsin/elastase-like serine proteases can also be further subdivided by the residues present in the Si pocket as described in Introduction to Protein Structure, Carl Branden and John Tooze, 1991 (Garland Publishing Inc) pages 231-241. The subdivisions are chymotrypsin-like (Gly-226, Ser-189 and Gly-216 in S1 pocket), trypsin-like (Gly-226, Asp-189 and Gly-216 in S1) and elastase-like (Val-226 and Thr-216 in S1) where the residues numbering is taken from the standard chymotrypsin numbering. The trypsin-like serine proteases prefer substrates which place either Lys or Arg in the S1 pocket.
The serine proteases have a common catalytic mechanism characterized by a particularly reactive Ser residue at position 195 using the chymotrypsin numbering system. Examples of serine proteases include trypsin, tryptase, chymotrypsin, elastase, thrombin, plasmin, kallikrein, Complement C1, acrosomal protease, lysosomal protease, cocoonase, α-lytic protease, protease A, protease B, serine carboxypeptidase π, subtilisin, urokinase (uPA), Factor Vila, Factor IXa, and Factor Xa. The serine proteases have been investigated extensively for many years and are a major focus of research as a drug target due to their role in regulating a wide variety of physiological processes.
Processes involving serine proteases include coagulation, fibrinolysis, fertilization, development, malignancy, neuromuscular patterning and inflammation. It is well known that these compounds inhibit a variety of circulating proteases as well as proteases that are activated or released in tissue. It is also known that serine protease inhibitors inhibit critical cellular processes, such as adhesion, migration, free radical production and apoptosis. In addition, animal experiments indicate that intravenously administered serine protease inhibitors, variants or cells expressing serine protease inhibitors, provide protection against tissue damage.
Serine protease inhibitors have also been predicted to have potential beneficial uses in the treatment of disease in a wide variety of clinical areas such as oncology, hematology, neurology, pulmonary medicine, immunology, inflammation and infectious disease. Serine protease inhibitors may also be beneficial in the treatment of thrombotic diseases, asthma, emphysema, cirrhosis, arthritis, carcinoma, melanoma, restenosis, atheroma, trauma, shock and reperfusion injury. A useful review is found in Expert Opin. Ther. Patents (2002), 12(8). Serine protease inhibitors are disclosed in US published patent applications US 2003/0100089 and 2004/0180371 and in U.S. Pat. Nos. 6,784,182, 6,656,911, 6,656,910, 6,608,175, 6,534,495 and 6,472,393.
Leukopenia refers to a decrease in the total leukocyte count below about 4.0×109 cells/L. Usually, the reduction is a result of a decrease in the number of polymorphonuclear neutrophils (PMN) (neutropenia), their numbers being usually less than 2.0×109 cells/L and frequently below 1.0×109 cells/L. Neutropenia may result from viral infections (e.g. influenza, measles, hepatitis virus, chickenpox, dengue and yellow fever, HIV) or from overwhelming bacterial infections including miliary tuberculosis and septicemia. Furthermore, neutropenia develops due to irradiation or treatment with drugs used e.g. in chemotherapy of malignant diseases or vasculitis and autoimmune diseases. Examples for drug-induced neutropenia are sulfonamides, antithyroid drugs, antihistamines, antimicrobial agents, phenothiazines and various analgesics, sedatives and anti-inflammatory agents or various toxic chemicals. Induction of cell death by infectious agents, drugs and toxic chemicals or antibodies may affect neutrophils and/or their precursor cells in the bone marrow. Antibodies to cells of the myeloid lineage are seen in immune mediated diseases such as systemic lupus erythematodes or juvenile rheumatoid arthritis. Last but not least various forms of congenital neutropenia have been described. Neutropenia results not only from damage of PMN in the circulation, but also from damage of stem cells and mitotic cells in the bone marrow by infectious agents, drugs, irradiation and toxic chemicals or due to slowing of cell divisions, blockade of DNA strand duplication, RNA formation or disruption of the microtubules of the mitotic spindle.
Neutropenia e.g. due to chemotherapy for hematologic malignancies, solid tumors or carcinomas leads to an impaired host response with significant morbidity and mortality due to infections. For example chemotherapy of early breast cancer with cyclophosphamide, methotrexate and fluorouracil results in neutropenic events in 30% of the patients with sepsis with requirement for delay of further anti-cancer treatment or dose reduction. Dose reductions of 20-30% have been associated with lower complete response rates and shortened survival in patients with lymphoma or with inferior relapse—free survival. Despite of improvements in antibacterial therapy for neutropenic sepsis, each year approximately 5% of patients receiving myelotoxic chemotherapy die due to infection related complications.
In-vitro handling of neutrophils and their precursor cells e.g. for gene therapy or for preparation of infusions of neutrophils is associated with an increase of cell death due to induction of apoptosis of myeloid cells.
Present agents used for the treatment of neutropenia include G-CSF, GM-CSF and G-CSF conjugated to polyethylene glycol as pegulated G-CSF. Despite the availability and considerable efficacy of the above approved agents in reducing the risk of neutropenia and its complications remain significant issues in oncology. Rarely rupture of the spleen but more frequently increase of the spleen volume, disturbances of gas exchange in the lung and single cases of acute injury stroke and myocardial infarction have been observed in healthy donors receiving G-CSF for harvesting peripheral blood stem cells. The evidences that G-CSF causes myelodysplastic syndromes and acute myeloic leukemia are less clear and need to be analyzed in further prospective long-term studies.
Although these approaches have shown promise, there is a need of improved therapeutic, prophylactic or diagnostic approaches for the treatment of neutropenia. The present invention provides an improved and reliable method for the treatment, diagnosis or prophylaxis of neutropenia comprising the administration to a subject in need thereof of a therapeutically effective amount of a Serine protease inhibitor.
These and other objects as will be apparent from the foregoing have been achieved by the present invention.